package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;



public class SimpleExecutor implements Executor {
    private PreparedStatement preparedStatement;

    public void before(Configuration configuration, MappedStatement mappedStatement, Object... params) throws  Exception{
        //1.注册驱动，获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句    select * from user where id= #{id} and username= #{username}
        String sql = mappedStatement.getSql();
        //转换sql语句   select * from user where id= ？and username= ？，还需对#{}中的值进行解析存储
        BoundSql boundSql=getBoundSql(sql);

        //3 获取预处理对象 preparedStatement
        preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4 设置参数
        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass=getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for(int i = 0; i < parameterMappingList.size();i++){
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            //获取属性对象
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }

    }
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception{
        before(configuration,mappedStatement,params);
        //5 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();

        //6 封装返回结果集
        while(resultSet.next()){
            Object o = resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            //columnCount  列数
            for(int i =1;i<=metaData.getColumnCount();i++){
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);
                //使用反射，根据数据库表与实体的对应关系完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }


        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception{
        before(configuration,mappedStatement,params);
        //5 执行sql
        int i = preparedStatement.executeUpdate();
//        ResultSet resultSet = preparedStatement.executeQuery();
//        String resultType = mappedStatement.getResultType();
//        Class<?> resultTypeClass = getClassType(resultType);
        return i;
    }



    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if(parameterType!=null){
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }


    /**
     * 完成对#{}的解析工作：1 将#{}使用？进行代替 2 解析出#{}中的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }


}
